1198818991 has 2 divisors, whose sum is σ = 1198818992. Its totient is φ = 1198818990.

The previous prime is 1198818979. The next prime is 1198819001. The reversal of 1198818991 is 1998188911.

It is a strong prime.

It is an emirp because it is prime and its reverse (1998188911) is a distict prime. It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 1668188611 and 1168818661.

It is a cyclic number.

It is not a de Polignac number, because 1198818991 - 2¹³ = 1198810799 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1198818931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 599409495 + 599409496.

It is an arithmetic number, because the mean of its divisors is an integer number (599409496).

Almost surely, 2^1198818991 is an apocalyptic number.

1198818991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1198818991 is an equidigital number, since it uses as much as digits as its factorization.

1198818991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 373248, while the sum is 55.

The square root of 1198818991 is about 34623.9655585550. The cubic root of 1198818991 is about 1062.3098410506.

The spelling of 1198818991 in words is "one billion, one hundred ninety-eight million, eight hundred eighteen thousand, nine hundred ninety-one".